Pattern-wise thermal transfer of materials from donor sheets to receptor substrates has been proposed for a wide variety of applications. For example, materials can be selectively thermally transferred to form elements useful in electronic displays and other devices. Specifically, selective thermal transfer of color filters, black matrix, spacers, polarizers, conductive layers, transistors, phosphors, and organic electroluminescent materials have all been proposed.
Thermal transfer of some materials can be problematic, especially for high resolution applications and for transfer processes where adhesion of the transferred materials to the receptor upon transfer (or other such transfer-related properties) is an issue. To address these issues, adhesive layers, or other so-called transfer assist layers, can be deposited on receptors or on transfer layers prior to thermal transfer. However, when transferring a material or materials to make an electronically active device such as a transistor or an organic electroluminescent device, the adhesive or transfer assist layer will often be disposed between layers of the finished device. In such a case, it may be important to provide a transfer assist layer that also provides functionality, or in any case does not undesirably hinder device operability. The present invention provides an active primer layer that can both improve transfer properties and maintain device functionality. Furthermore, the present invention contemplates an active primer that includes an electronically active material dispersed in a binder where the electronically active material can be selected for functionality (e.g., given the specific device being made, construction of the device, materials of the device, and so on) and the binder can be selected for transfer assist properties (e.g., given the materials being transferred, details of the receptor substrate, and so on). The present invention also contemplates active primers that include polymers having active materials pendant to polymer backbone, that is polymers functionalized by covalent bonding of active materials. For the purposes of describing the present invention, the phrase xe2x80x9cactive material dispersed in a binderxe2x80x9d and other such descriptions of the active primer expressly include polymers functionalized with active materials.
By way of example, active primer layers of the present invention can be useful in improving the transfer of light emitting polymers to form organic electroluminescent devices where the active material of the primer layer provides a charge transport function.
In one embodiment, the present invention provides a process for patterning a layer of an electronic device including the steps of disposing an active primer between a receptor substrate and a thermal transfer donor and selectively thermally transferring a portion of a transfer layer that includes a material component of the electronic device from the donor to the receptor to form at least a portion of the electronic device. The active primer includes an electronically active material dispersed in a binder, the binder being selected to promote selective thermal transfer of the transfer layer to the receptor, and the electronically active material being selected to maintain operability of the electronic device.
In another embodiment, the present invention provides a process for patterning a plurality of organic electroluminescent devices on a receptor. In the process, a receptor is provided that includes a plurality of anodes disposed on a surface thereof, and a thermal transfer donor element is provided that includes a base substrate and a transfer layer. The transfer layer includes an organic electroluminescent material. Next, an active primer is disposed between the anode surface of the receptor substrate and the transfer layer of the donor element. The active primer includes an electronically active material dispersed in a binder, the binder selected to promote thermal transfer of the transfer layer to the receptor. Next, the transfer layer is selectively thermally transferred from the donor element to the receptor to form a pattern of the organic electroluminescent material on the receptor. Next, a cathode material is deposited on the pattern of the organic electroluminescent material to form a plurality of organic electroluminescent devices on the receptor, each of the devices including in the following order one of the anodes, a portion of the active primer, a portion of the organic electroluminescent material, and a portion of the cathode.
In yet another embodiment, the present invention provides a thermal transfer donor element that includes a base substrate, a thermal transfer layer capable of being selectively thermally transferred from the donor element to form at least a portion of an electronic device, and an active primer disposed on the thermal transfer layer as the outermost layer of the donor element. The active primer includes an electronically active material dispersed in a binder, the binder being selected to promote selective thermal transfer of the transfer layer to a receptor, and the electronically active material being selected to maintain operability of the electronic device.